Warning device for high pressure vessels

ABSTRACT

The warning device includes a stop movable between door latching and unlatching positions under the control of a manually manipulated handle operator after an initial period of handle operator movement, during which the latter serves to open a vessel pressure exhaust valve. A modified construction features a fluid cylinder unit coupled between the vessel and the stop in order to constrain movements of the stop until pressure within the vessel is reduced to a predetermined safe value.

United States Patent [191 Piegza WARNING DEVICE FOR HIGH PRESSURE VESSELS [75] Inventor: Henry J. Piegza, Clarence, NY.

[73] Assignee: WSF Industries, Inc., Tonawanda,

22 Filed: Dec. 4, 1972 21 Appl. No.: 312,186

[52] US. Cl. 220/55.3, 137/584, 220/40 S, 220/55 Y, 292/304 51 i t. C1,." A47j 27/08, F16k 45/00, E050 19/00 [58] Field ofSearch 220/40 R, 40 S, 55.3, 220/DIG. 20; 137/584; 292/304 [56] References Cited UNITED STATES PATENTS 658,343 9/1900 Clark 292/304 1,208,041 12/1916 Steere 220/55.7 1,534,131 4/1925 McBride 220/40 R 2,599,072 6/1952 Schweiso 220/55.3 2,706,999 4/1955 Pickard 137/584 [4 1 Aug. 20, 1974 2,841,308 7/1958 Weicker 220/40 R 3,653,533 4/1972 Mortensen 220/40 R FOREIGN PATENTS OR APPLICATIONS 412,700 6/1934 Great Britain 220/55.3

Primary Examiner-William J. Price Assistant ExaminerAllan N. Shoap Attorney, Agent, or Firm-Bean & Bean [5 7 ABSTRACT The warning device includes a stop movable between door latching and unlatching positions under the control of a manually manipulated handle operator after an initial period of handle operator movement, during which the latter serves to open a vessel pressure exhaust valve. A modified construction features a fluid cylinder unit coupled between the vessel and the stop in order to constrain movements of the stop until pressure within the vessel is reduced to a predetermined safe value.

10 Claims, 6 Drawing Figures PATENTEnAuczolsu S'EEIIUZ WARNING DEVICE FOR HIGH PRESSURE VESSELS BACKGROUND OF THE INVENTION Many manually operable devices have been proposed for use in preventing the unlocking of the closure mechanism of a pressure vessel when a pressure condition exists within a vessel in order to prevent violent opening" of the vessel and possible uncontrolled discharge of the vessel contents. As by way of specific illustration, reference is made to U.S. Pat. Nos. 2,706,999 and 3,107,810; British Patents 302,787 and 412,700 and German Patent 828,178.

These prior art devices normally include a manually operated handle, which serves to open a vessel exhaust valve, as an associated stop is moved between vessel closure or door latching and unlatching positions; the valve when opened permitting controlled reduction in vessel pressure by venting the vessel to atmosphere. In some constructions, any gas escaping through the open valve is employed to drive a mechanical signaling device, such as a whistle, in order to give a positive warning of the existence of an undesired pressure condition within the vessel.

A problem encountered by many prior art devices of this general type is that the stop is removed from its unlatching position before the handle operator has completed its movement to a point at which the valve has been opened sufficiently to reduce vessel pressure and- /or produce a desired warning signal. Thus, if a careless worker should fail to move the handle operator through its full range of unlatching movement, there is a possibility that the door will be released while the pressure condition exists within the vessel. In other words, the fact that the handle operator has been partially displaced from its fully latched position may give a false visual impression that the vessel has been vented and that it is safe to open the door.

SUMMARY OF THE INVENTION The present invention relates to an improved warning device for high pressure vessels, which insures that a warning of the existence of an undesired pressure condition within a pressure vessel is given before the vessel door is released for opening movement.

For purposes of illustration, the device of the present invention will be specifically disclosed as having utility in association with pressure vessel closures of the type described for instance in U.S. Pat. Nos. 2,841,308 and 3,107,810, wherein the vessel door is suitably mounted adjacent an open end of the vessel for movement between opened and closed positions, and a locking ring is rotatably supported adjacent the open end of the vessel for releasably retaining the door locked in closed position. In this type of door closure, the door and locking ring are each provided with wedge shaped cam surfaces, which cooperate after the door has been substantially closed to firmly seat a sealing surface of the door in fluid-pressure sealing relationship relative to a sealing surface bounding the open end of the vessel, as the locking ring is rotated relative to both the door and the vessel between its door unlocking and locking positrons.

More specifically, the warning device of the present invention features a manually manipulatable handle operator, which is movable between latching and un latching positions through an intermediate position and coupled to a vessel exhaust valve such that opening of the valve is effected during movement of the handle operator from its latching to its intermediate position and is retained in open condition during movement of the handle operator from such intermediate position into its fully unlatched position; and a stop movable between latching and unlatching positions under the control of the handle operator only during movement of the latter between its intermediate and fully unlatched positions. The stop, when in its fully latched position, is arranged to be engaged by an abutment carried by the locking ring and to in turn engage with a vessel carried bracket, whereby forces tending to oppose unlocking rotational movements of the locking ring are transferred to the vessel through the bracket.

In one form of the present invention, a fluid cylinder unit is employed to couple the stop to the vessel in order to constrain movement of the stop away from its latched positionuntil the pressure within said vessel is reduced to a predetermined valve.

DRAWINGS The nature and mode of operation of the present invention will now be more fully described in the following detailed description taken with the accompanying drawings wherein:

FIG. 1 is a fragmentary perspective view of the high pressure vessel employing the warning device of the present invention;

FIG. 2 is a side elevational view of the warning device shown in FIG. 1;

FIG. 3 is a view similar to FIG. 2, but showing the device of the present invention in door unlatched positron;

FIG. 4 is a sectional view taken 4-4 in FIG. 2;

FIG. 5 is a sectional view taken 5-5 in FIG. 2; and

FIG. 6 is a view similar to FIG. 2, but illustrating an alternative form of the present invention.

DETAILED DESCRIPTION For purposes of illustration, the warning device of the present invention, which is generally designated as 10 in the drawings, will be described as having use in combination with a conventional closure mechanism for high pressure vessels of the type disclosed for example in U.S. Pat. Nos. 2,841,308 and 3,107,810. A vessel of this type is generally designated as 12 in FIG. 1 and includes a cylindrical shell 14 and a vessel closure mechanism defined by a door 16 for selectively closing an open end of the shell, and a locking ring 18, which is supported adjacent the open end of the shell for rotational movements between door locking and unlocking positions, as indicated by arrow 20 in FIGS. 1 and 4. In this type of closure mechanism, the locking ring is formed with lugs 22, which are annularly spaced apart in order to permit passage therebetween of door carried lugs, not shown, when the door is moved into its closed position, while the locking ring is in its door unlocking or releasing position. The ring and door lugs carry wedge shaped cam surfaces, also not shown, which cooperate to firmly seat a sealing surface of the door in fluid-pressure sealed relationship relative to a sealing surface bounding the open end of the shell when the locking ring is subsequently rotated relative generally along line generally along line to both door and shell into its door locking position. Door 16 may be supported for movement relative to the shell in any desired manner.

As in above mentioned US. Pat. No. 3,107,810, the preferred form of warning device includes a suitable abutment 24, which is weld or otherwise affixed for movement with locking ring 18; and a valve 26 for controlling venting of vessel 12 through a conduit 28. When the pressurizing gas is harmless, the vessel may be vented directly to atmosphere. While the sound naturally produced by vented pressurized gas may be re lied upon to give an audible warning of the existence of an undesired pressure condition within the vessel, it is preferable to pass the vented gas through a mechanical sound generating device, such as a whistle designated as W only in FIG. 6, in order to provide a clear and unmistakable warning to workmen in the area of the vessel.

Now referring particularly to FIGS. 1-5, it will be seen that the improved warning device of the present invention features a high strength metal, elongated shear bar or stop 30 having'an inclined end surface 32 and an adjacently disposed mounting flange 34; and a handle operator 36. Mounting flange 34 is freely journaled upon and handle operator 36 is affixed, as by set screw 38, for rotation with a valve operator or stem 40 whose respective ends are journaled within valve 26 and vessel shell mounted support bracket 42, as best shown in FIG. 5. In the illustrated construction, valve 26 is a ball type valve, which is maintained in a fully closed condition by the handle operator 36 when the latter is in its fully latched position shown in full line in FIGS. 1 and 2 and phantom line in FIG. 3, and is moved into a fully or substantially fully opened condition by the handle operator when the latter is moved into an intermediate position thereof shown in phantom line in FIG. 3. The intermediate position of handle operator 36 is determined by engagement of the flat lower surface of handle operator base portion 36a with shear bar inclined end surface 32. Valve 26 remains in at least a substantially open condition during continued movement of handle operator 36 from its intermediate position into its fully unlatched position shown in. full line in FIG. 3. The fully unlatched position of the handle operator may be determined by the physical construction of valve 26, eg. the degree its stem 40 is permitted to rotate, or by engagement of the handle operator with a suitable limiting abutment, not shown, which may be defined for instance by support bracket 42.

Warning device 10 additionally includes a rugged or high strength metal, essentially J-shaped stop or abutment bracket 44, which has its base leg 44a weld affixed to vessel shell 14. Bracket legs 44a and 44b and bracket leg connecting flange 44c cooperate to define an open ended slot 46, which is dimensioned to freely receive abutment 24, as locking ring 18 is rotated between its door locking and unlocking positions shown in full and phantom line in FIG. 4, respectively. Legs 44a, 44b and flange 44c are also formed to define a side opening slot 48, which is disposed to extend transversely of slot 46 and have its leading surface and trailing or abutment surfaces 480 and 48b in the direction of locking ring rotation, respectively, arranged substan tially parallel to the leading or forward end abutment face 240 of abutment 24. Slot surfaces 48a and 48b are spaced apart sufficiently to freely receive shear bar 30 and base 36a of handle operator 36 therebetween, and

in the arrangement illustrated leading surface 48a is disposed in a substantially coplanar relationship with abutment face 24a when the locking ring is in its door locking position. Thus, when shear bar 30 is disposed in its fully latched position, as shown in full line in FIGS. 1, 2 and 4 and phantom line in FIG. 3, it extends transversely within slot 46 to position its leading side abutment surface 30a for engagement by abutment face 24a.

If any attempt is made to move locking ring 18 into its door unlocked position while shear bar 30 is in its fully latched position, the pressure of abutment face 240 on shear bar leading side surface 30a will force the trailing or opposite surface 30b of the shear bar into engagement with slot trailing surface 48b, which is defined by bracket legs 44a and 44b, and bracket 44 will thereupon constrain further rotation of the locking ring. It will be understood that the extent of rotational movement of the locking ring permitted by device 10 when latched is quite small and well below that which may result in interference with or destruction of fluidpressure seal between the sealing surfaces of the door and vessel shell. With this construction, substantially all forces opposing unlocking rotations of locking ring 18 are carried by shear bar 30 to bracket 44 and thereby directly into the vessel shell; the slight amount of movement of shear bar 30 relative to valve operator 40 which is permitted by their loose pivotal connection being effective to isolate the valve operator from such forces.

In that the width or transverse dimension of shear bar abutment surface 30a is the same as or slightly greater than the radially directed dimension of abutment face 24a, all shear forces are borne by the shear bar, and handle operator base 36 when seated within slot 48 in its fully latched position, merely serves as a visual indication that the shear bar is in its latched position. Thus, the handle operator may be of relatively light weight and inexpensive design, such as would be afforded by a simple aluminum casting.

If desired, suitable means, such as spring biased balldetent devices 50 and 52 may be employed to releasably retain shear bar 30 and handle operator 36 seated in their fully latched position. Also, while not specifically illustrated, it will be understood that suitable means may be employed to normally bias the shear bar and/or the handle operator towards their fully latched positions in order to insure that device 10 is fully latched at all times except when it is intentionally operated by manipulation of the handle operator.

When desired to release locking ring 18 for movement into its door unlocking position, it is merely necessary for an operator to move or pull the handle operator from its fully latched position illustrated in FIG. 2 into its intermediate position illustrated in phantom line in FIG. 3 and finally into its fully unlatched position illustrated in full line in FIG. 3. During movement of the handle operator into its intermediate position to effect opening of valve 26, shear bar 30 remains seated in its fully latched position as indicated in phantom line in FIG. 3, whereby to insure that latching device 10 remains latched until after the valve is opened to an extent sufficient to provide an audible warning that there exists an undesired pressure condition within the vessel. In the absence of a warning signal, the operator knows that it is then safe to fully unlatch device 10 and accordingly moves the handle operator from its intermediate position into its fully unlatched position. During this latter period of movement, shear bar 30 is moved by the handle operator from its fully latched into its fully unlatched position as indicated in FIG. 3, due to engagement of the lower surface of the handle operator base 36a with shear bar inclined end surface 32. Preferably, the inclination of surface 32 is such as to insure full faceto-face contact between such surface and the bottom surface of base portion 36a, during the whole of shear bar swinging movement.

In the illustrated construction, an operator is made to feel movement of the handle operator past its intermediate position, due to the force which must be applied to the handle operator to disengage the shear bar from detent 50 and whatever bias which may be employed to normally move the shear bar towards its fully latched position. For installations wherein locking ring 18 rotates within an essentially vertically disposed plane and shear bar 30 is essentially horizontally disposed when in fully latched position, the weight of the shear bar alone may be employed as the bias and serve to give a clear warning to an operator that the handle operator has been moved into its intermediate position.

Device may be returned to latched position by merely returning handle operator 36 to its fully latched position; shear bar 30 automatically returning to its fully latched position by the time that the handle operator is returned to its intermediate position if the above mentioned bias is provided, but otherwise being forced to return to its latched position by engagement with the lower surface of handle operator base 36a as the handle operator is moved between its intermediate and latched positions.

FIG. 6 illustrates a modified form of the present invention wherein a fluid cylinder unit 60 comprising a shear bar connected piston 62 and a vessel shell connected cylinder 64 is employed to constrain movement of the shear bar away from its fully latched position when an undesired pressure condition exists within the vessel. To this end, one end of cylinder 64 is placed in flow communication with the interior of the vessel, as for instance by branch conduit 66 connected into con duit 28 upstream of valve 26, while the other end is placed in communication with the atmosphere via aperture 68. With this construction, any pressure condition existing within the vessel is employed to positively retain shear bar 30 in its fully latched position during normal operation of the vessel and until handle operator 36 has been manipulated to maintain valve 26 in an open condition for a period of time sufficient to reduce vessel pressure, and thus the pressure within conduit 28 and branch conduit 66, to a predetermined safe value, which will normally vary depending upon the size and weight of door 16, but may be essentially zero. When long term exposure to vessel environmental conditions would be destructive to cylinder unit 60, the branch conduit may be connected into conduit extension 28' intermediate valve 26 and whistle W, as indicated in phantom line at 66 In this construction, the cylinder unit is operated by a back pressure condition created downstream of the whistle device after valve 26 has been opened.

Since for most installations cylinder unit 60 will necessarily be small, it might be possible for a strong operator to force the shear bar from its fully latched position against the bias established by the unit particularly when vessel internal pressure has been reduced to a relatively low, but none the less dangerous value. However, until vessel pressure is reduced to substantially zero, unit 60 will normally remain effective to automatically bias the shear bar for return to its latched position, as soon as the operator releases the handle operator. Since for conventional installations the locking ring rotation controls are relatively remote from the vessel, unit 60 is normally effective in preventing a single operator from initiating opening movements of the closure mechanism, while the safety latch device is improperly overridden.

To guard against all error in judgement on the part of the operator, a suitable pressure amplifier placed for instance within line 66, as indicated in phantom at 70, would be employed to supply the cylinder unit with an operating pressure substantially in excess of above mentioned predetermined safe value. In a typical installation, the amplifier would be connected to a suitable high pressure fluid source and include a valve operable in response to vessel pressure-no-pressure conditions to selectively place unit 60 in communication with the fluid source or exhaust the unit. In this arrangement,

the fluid source may be liquid or gas, as desired. Also, it is contemplated that means other than a cylinder unit, which is indirectly responsive to sensed vessel pressure, may be employed for retarding movement of the shear bar from its latched position.

I claim:

1. In a pressure vessel having a closure mechanism, a manually operable latching device movable between latching and unlatching positions for releasably retaining said closure mechanism in vessel closed condition, and a vessel exhaust valve operably associated with said latching device whereby when said latching device is in its latching position to retain said closure mechanism in vessel closed condition said valve is closed and when said latching device is in its unlatching position to release said closure mechanism from said vessel closed condition said valve is open, the improvement wherein said latching device comprises in combination:

manually operable handle means movable between latching and unlatching positions through an intermediate position, said handle means being coupled to said valve whereby to open said valve during movement of said handle means from its latching position into its intermediate position and retain said valve in open condition during movement of said handle means from its intermediate position into its unlatching position; and

stop means movable between latching and unlatching positions thereof, said stop means when in latching position being disposed for abutting engagement by said closure mechanism for retaining same in said vessel closed condition and when in unlatching position being removed from abutting engagement with said closure mechanism for releasing same from said vessel closed condition, and said handle means driving said stop means from latching into unlatching positions thereof only during movement of said handle means from its intermediate position into its unlatching position.

2. The improvement according to claim 1, wherein said latching device includes constraining means tending to constrain movement of said stop means from its latching position until pressure within said vessel is reduced to a predetermined safe value.

3. The improvement according to claim 2, wherein said constraining means includes a fluid cylinder unit having a piston fixed to one of said vessel and said stop means and a cylinder fixed to the other of said vessel and said stop means, and means for applying fluid pressure to said fluid cylinder unit when pressure within said vessel is in excess of said predetermined safe value thereby tending to constrain relative movement between said piston and said cylinder whereby to constrain movement of said stop means from its latching position.

4. The improvement according to claim 3, wherein said means for applying fluid pressure to said fluid cylinder unit places said fluid cylinder unit in direct flow communication with said vessel.

5. The improvement according to claim 3, wherein an audible sound producing device is connected by conduit means to said valve, said audible sound producing device is adapted to be driven by fluid escaping from said vessel through said valve when open, and said means for applying fluid pressure to said fluid cylinder unit includes conduit means for placing said fluid cylinder unit in flow communication with the first said conduit means.

6. The improvement according to claim 1, wherein said latching device includes means to releasably retain said handle means in said latching position thereof.

7. The improvement according to claim 1, wherein said handle means is fixed for rotation with an operator for said valve, said stop means is journaled on said valve operator, and said handle means and stop means includes surface portions spaced one from another when said handle means and said stop means are in their latching positions, said handle means surface portion being positioned in abutting engagement with said stop means surface portion during movement of said handle means from its latching position towards its unlatching position whereby to define said intermediate position thereof, and said surface portions thereafter cooperating to effect conjunctive movement of said stop means and said handle means whereby as said, handle means moves from its intermediate position into its unlatching position said stop means is moved from its latched position into its unlatching position:

8. The improvement according to claim 7, wherein; said latching device includes a fluid cylinder unit having a piston fixed to one of said vessel and said, stop means and a cylinder fixed to the other of said vessel and said stop means, and means for applying fluid pressure to said fluid cylinder unit when pressure;

within said vessel is in excess of a predetermined safe value thereby tending to constrain relative movement between said piston and said cylinder whereby to constrain movement of said stop means from its latching position.

9. In a high pressure vessel having a vessel shell defining an opening, a door adapted to close said opening, a locking ring carried by said vessel shell and surrounding said opening, said locking ring being capable of rotation through a small are between a first position, in which means cam'ed thereby engage cooperating means on said door to prevent its removal and a second position in which the means carried thereby disengage the means on said door to permit its removal, and a latching device for releasably pre-' venting rotation of said locking ring from its first to its second position, said latching device comprising in combination:

an abutment carried by said locking ring and defining a bearing face arranged to face in the direction of rotation of said locking ring from its first position to its second position;

a valve having an operator rotatable between valve closed and open conditions;

conduit means for supporting said valve on said vessel shell and for placing said valve in flow communication with the interior of said vessel;

manually operable handle means fixed to said valve operator for rotation therewith between a latching position and an unlatching position through an intermediate position, said valve being maintained in closed condition when said handle means is in its latching position and being moved into open condition upon movement of said'handle means into its intermediate position and being maintained in at least substantially open condition during movement of said handle means into its unlatching position; and

stop means journaled on said valve opefidr for rota tional movement relative thereto between latching and unlatching positions, said stop means when in its latching position being disposed within said;

other slot to position a leading surface thereof immediately adjacent said other slot leading surface. and for abutment by said bearing face of said abut ment and to position a trailing surface thereof immediately adjacent said other slot abutment surface, whereby to prevent rotation of said locking ring from said first into said second positions thereof by engagement of said stop means leadingsurface with said bearing face and resultant engagement of said stop means trailing surface with said other slot abutment surface, said stop means and said handle means having cooperating surface portions spaced one from another when said handle means and said stop means are in said latching positions thereof, said handle means surface portion being positioned in abutting engagement with said stop means surface portion during movement of said handle means from said latching into said unlatching positions thereof whereby to define said intermediate position, and said cooperating surface portions thereafter cooperating to effect conjunctive movement of said stop means and said handle means whereby as said handle means moves from its intermediate position into its unlatching position said stop means is forced to move from its latching position into its unlatching position.

10. The improvement according to claim 9, wherein said latching device includes a fluid cylinder unit hav ing a piston fixed to one of said vessel and said stop means and a cylinder fixed to the other of said vessel and said stop means, and means for applying fluid pressure to said fluid cylinder unit when pressure within said vessel is in excess of a predetermined safe value thereby tending to constrain relative movement between said piston and said cylinder whereby to con- 

1. In a pressure vessel having a closure mechanism, a manually operable latching device movable between latching and unlatching positions for releasably retaining said closure mechanism in vessel closed condition, and a vessel exhaust valve operably associated with said latching device whereby when said latching device is in its latching position to retain said closure mechanism in vessel closed condition said valve is closed and when said latching device is in its unlatching position to release said closure mechanism from said vessel closed condition said valve is open, the improvement wherein said latching device comprises in combination: manually operable handle means movable between latching and unlatching positions through an intermediate position, said handle means being coupled to said valve whereby to open said valve during movement of said handle means from its latching position into its intermediate position and retain said valve in open condition during movement of said handle means from its intermediate position into its unlatching position; and stop means movable between latching and unlatching positions thereof, said stop means when in latching position being disposed for abutting engagement by said closure mechanism for retaining same in said vessel closed condition and when in unlatching position being removed from abutting engagement with said closure mechanism for releasing same from said vessel closed condition, and said handle means driving said stop means from latching into unlatching positions thereof only during movement of said handle means from its intermediate position into its unlatching position.
 2. The improvement according to claim 1, wherein said latching device includes constraining means tending to constrain movement of said stop means from its latching position until pressure within said vessel is reduced to a predetermined safe value.
 3. The improvement according to claim 2, wherein said constraining means includes a fluid cylinder unit having a piston fixed to one of said vessel and said stop means and a cylinder fixed to the other of said vessel and said stop means, and means for applying fluid pressure to said fluid cylinder unit when pressure within said vessel is in excess of said predetermined safe value thereby tending to constrain relative movement between said piston and said cylinder whereby to constrain movement of said stop means from its latching position.
 4. The improvement according to claim 3, wherein said means for applying fluid pressure to said fluid cylinder unit places said fluid cylinder unit in direct flow communication with said vessel.
 5. The improvement according to claim 3, wherein an audible sound producing device is connected by conduit means to said valve, said audible sound producing device is adapted to be driven by fluid escaping from said vessel through said valve when open, and said means for applying fluid pressure to said fluid cylinder unit includes conduit means for placing said fluid cylinder unit in flow communication with the first said conduit means.
 6. The improvement according to claim 1, wherein said latching device includes means to releasably retain said handle means in said latching position thereof.
 7. The improvement according to claim 1, wherein said handle means is fixed for rotation with an operator for said valve, said stop means is journaled on said valve operator, and said handle means and stop means includes surface portions spaced one from another when said handle means and said stop means are in their latching positions, said handle means surface portion being positioned in abutting engagement with said stop means surface portion during movement of said handle means from its latching position towards its unlatching position whereby to define said intermediate position thereof, and said surface portions thereafter cooperating to effect conjunctive movement of said stop means and said handle means whereby as said handle means moves from its intermediate position Into its unlatching position said stop means is moved from its latched position into its unlatching position.
 8. The improvement according to claim 7, wherein said latching device includes a fluid cylinder unit having a piston fixed to one of said vessel and said stop means and a cylinder fixed to the other of said vessel and said stop means, and means for applying fluid pressure to said fluid cylinder unit when pressure within said vessel is in excess of a predetermined safe value thereby tending to constrain relative movement between said piston and said cylinder whereby to constrain movement of said stop means from its latching position.
 9. In a high pressure vessel having a vessel shell defining an opening, a door adapted to close said opening, a locking ring carried by said vessel shell and surrounding said opening, said locking ring being capable of rotation through a small arc between a first position in which means carried thereby engage cooperating means on said door to prevent its removal and a second position in which the means carried thereby disengage the means on said door to permit its removal, and a latching device for releasably preventing rotation of said locking ring from its first to its second position, said latching device comprising in combination: an abutment carried by said locking ring and defining a bearing face arranged to face in the direction of rotation of said locking ring from its first position to its second position; a bracket fixed to said vessel shell adjacent said locking ring, said bracket defining an open ended slot for freely receiving said abutment during rotation of said locking ring and another slot arranged to extend transversely of said open ended slot in communication therewith, said other slot having leading and abutment surfaces spaced in the direction of rotation of said locking ring; a valve having an operator rotatable between valve closed and open conditions; conduit means for supporting said valve on said vessel shell and for placing said valve in flow communication with the interior of said vessel; manually operable handle means fixed to said valve operator for rotation therewith between a latching position and an unlatching position through an intermediate position, said valve being maintained in closed condition when said handle means is in its latching position and being moved into open condition upon movement of said handle means into its intermediate position and being maintained in at least substantially open condition during movement of said handle means into its unlatching position; and stop means journaled on said valve operator for rotational movement relative thereto between latching and unlatching positions, said stop means when in its latching position being disposed within said other slot to position a leading surface thereof immediately adjacent said other slot leading surface and for abutment by said bearing face of said abutment and to position a trailing surface thereof immediately adjacent said other slot abutment surface, whereby to prevent rotation of said locking ring from said first into said second positions thereof by engagement of said stop means leading surface with said bearing face and resultant engagement of said stop means trailing surface with said other slot abutment surface, said stop means and said handle means having cooperating surface portions spaced one from another when said handle means and said stop means are in said latching positions thereof, said handle means surface portion being positioned in abutting engagement with said stop means surface portion during movement of said handle means from said latching into said unlatching positions thereof whereby to define said intermediate position, and said cooperating surface portions thereafter cooperating to effect conjunctive movement of said stop means and said handle means whereby as said handle means moves from its intermediate position into its unlatching position said stop means is forced to Move from its latching position into its unlatching position.
 10. The improvement according to claim 9, wherein said latching device includes a fluid cylinder unit having a piston fixed to one of said vessel and said stop means and a cylinder fixed to the other of said vessel and said stop means, and means for applying fluid pressure to said fluid cylinder unit when pressure within said vessel is in excess of a predetermined safe value thereby tending to constrain relative movement between said piston and said cylinder whereby to constrain movement of said stop means from its latching position. 